Inverse-Designed Tellurite Devices for Polarization Control

Tellurite glasses are of high interest in integrated photonics for sensing and, in particular, telecommunications applications, where they serve as key materials for amplification and mid-IR light sources due to their wide transparent window, thermal and mechanical stability, and high optical nonlinearity. In this work, we present two inverse-designed devices for polarization management on a tellurium dioxide platform: a TM-pass polarizer and a polarization beam splitter. The TM-pass polarizer achieves an average simulated transmission efficiency of −0.6 dB and an polarization crosstalk below −20.9 dB across the entire C-band, with a footprint of only 24 μm × 6 μm. The polarizationbeam splitter has an ultra-compact footprint of 28 μm × 6 μmand achieves average TE and TM transmission efficiencies ofapproximately −0.4 dB, with crosstalk below −18.3 dB and−27.2 dB, respectively. These are the first freeform devicesdemonstrated on a tellurium dioxide platform, exhibiting strongrobustness to fabrication variations and showcasing the versatilityof the platform beyond nonlinear applications.